1. Field:
This invention relates to apparatus for use in performing exercises. More particularly, this invention discloses a resistance system for use with exercise machines including rowing exercise machines.
2. State of the Art:
Exercise machines (e.g., rowing machines, lift machines, multi-gyms) in wide spread use today typically employ some type of structure to surmountably resist movement so that the user exercises various muscle groups in attempting to overcome the resistance. For example, the GYMPAK.sup..TM., manufactured by Diversified Products Corporation of Opelika, Ala., has a handle connected via an elevated pulley to ground level weights which are selected by the user as a resistance to be overcome by the user. U.S. Pat. No. 4,477,071 shows a rowing exercise machine in which a pair of hydraulic cylinders are used to provide resistance to movement of levers by the arms of a user.
As noted above, the resistance systems for these exercise machines frequently rely upon gravity acting upon selectable weights to provide variable resistance and upon hydraulic cylinders or springs in which a variable or adjustable lever dimension is employed such to vary the resistance as that shown in U.S. Pat. No. 4,477,071. Systems using selectable weights inevitably require some type of strong support structure to support the weight and space to allow movement through a distance. Further, the static weight inhibits widespread use of the machine which must be carefully placed to ensure that its support surface will not be damaged and is sufficiently strong to support the overall weight of the machine.
From another perspective, machines of the type shown in U.S. Pat. No. 4,477,071 typically employ two arms and two cylinders which are duplicative and in turn costly. Such arrangements require some volume for shipping and for storage. Similarly, machines employing weights are typically bulky and require some volume for shipping and storage. For both hydraulic and gravity-weight systems, adjustment of the resistance can be effected but generally only by stopping the exercise to adjust the resistance (e.g., change lever arm length and/or add/subtract weight). In systems involving multiple handles, resistance can be difficult to adjust.
A resistance system for machines is needed which is reliable and which involves use of compact resistance means but which is lightweight and easy to adjust preferably while in use.